Stress tensor mesostructures for deterministic figuring of thin substrates

Abstract

Accessing the immense value of freeform surfaces for mass-sensitive applications such as space optics or metaform optical components requires fabrication processes that are suited to figuring thin substrates. We present stress tensor mesostructures for precisely correcting figure errors, even after microstructures or coatings have been applied to the optical surface. These mesostructures can be fabricated using standard semiconductor fabrication equipment. We introduce three different mesostructure types that each spatially control the three required stress tensor components over the surface of thin substrates, each offering relative advantages. We patterned all three mesostructures on the backsides of silicon wafers to demonstrate freeform figure generation and correction. Stress tensor mesostructures can enable low-cost accurate figuring of the thin substrates that will become increasingly important for lightweight and metasurface optics.